Experimental Study On Microbial Remediation Of Concrete Cracks

As a kind of building material,concrete has been widely used in construction,water conservancy,port and other industries.Due to the complicated engineering environment,the concrete often has structural cracks due to its low tensile strength,even with the development of cracks may lead to the destruction of the overall structure.Since the end of last century,a new type of concrete crack repair methods——Microbial Induced Calcium Carbonate Precipitation Repair Technology（MICP）was proposed,it is a microbial technology applied in the field of construction engineering,due to repairing cracks required the bacteria solution has good fluidity,during the repair process,the microbial metabolites and cement-based materials have good compatibility and interfacial strength,it has the potential of low energy consumption,green environmental protection and simple construction.In this paper,Sporosarcina pasteurii induced calcium carbonate deposition was used to repair concrete cracks.Through analyzing the repair process and the effect,the scientific basis of fracture bioremediation technology is provided.The main contents and results are as follows:First,the growth characteristics of Sporosarcina pasteurii in different pH environment,the adaptability after the abrupt change of environmental pH and the mineralization in different pH environment were studied.The results showed that the pH range of the growth of Sporosarcina pasteurii was 6¹1,the optimum value of pH was 9.Bacterias need 12h to rereach a stable period when the environment of the pH was changed suddently.In addition,bacteria can also be mineralized to produce calcium carbonate crystals in the high alkaline environment,but the morphology of calcium carbonate is different.Then,the cracks are repaired with different crack width,depth,angle of inclination and filling medium or not.The permeability coefficient of repaired concrete increases with the increase of crack width,increases and then decreases with the increase of fracture angle,but is little affected by the depth of the crack.When the medium is added into the crack,the best repair effect is achieved,and the permeability coefficient can reach 1.297×10^-9 m/s.The crack repair process of concrete is from outside to inside,and the calcium carbonate crystals produced in the cracks show spherical or spherical aggregates with different sizes.Finally,in order to simulate the irregularity of the real crack,the split cracks was repaired and the repair effect of the crack was observed.Calcium carbonate formed by microbial remediation of concrete cracks is very uneven,mainly concentrated in the opening of the cracks,the amount of calcium carbonate attached to cracks inside is quite few.